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NA Lean Tip in.

Muad'Dib

Muad'Dib

NAXJA Forum User
Location
Bend, Oregon
Hey guys.. got a question for ya..

I am having a problem with my RENIX Stroker that im looking for ideas on..

I have an issue with a Lean Tip-in. Especially when at a stop and then accelerating.

I know that with forced induction you can throw a 02 clamp or map clamp on it to help with this.. but im wondering what i might be able to do with a NA engine.

My assumption is that this has to do with my RENIX computer not able to cope with the extra air that is coming in through the intake. Id rather not build and implement a new ECU like Megasquirt.. but that may be my only option. Before i even consider going down that road i figured i would post here and see if anyone has any ideas on how to throw more fuel in past idle.

FWIW, its not much of an issue if an issue at all if i go WOT. However, if i do a part throttle launch thats when i will go lean. Not sure if there is a way to build something to help with this without doing a custom ECU (RENIX cant really be modified). I do have an adjustable MAP and AFPR... but they are tweaked just right for optimal WOT AFR's.

Thanks for the possible help!
 
Oh yeah for sure.. I have done that with Multiple TPS's. Even went as far as ordering a OEM TPS from the Dealer thinking that maybe all the after market ones were lazy.

That would be really the best way to describe it.. a lazy TPS. Lazy TPS that only affects the off idle range. FWIW, ive also checked the TPS output wire to the ECU ... little to no resistance.. so im pretty sure its not bad wiring.
 
Ever checked the sensor ground circuit resistance as described below?

Cruiser’s Renix Sensor Ground Test
　
This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.
Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.
Revised 06/12/2012
 
I suppose you could try it. You have to be careful because as the percentage goes up, the ECU sees it as partial throttle and you can have idle flare issues.

I'm wondering if his lean tip-in and wavering idle speed on coasting (another thread)are not somewhat related. That's why I suggested checking the sensor ground circuit for resistance. He might have already done that, but TPS is only one of the sensors that uses that circuit and the harness has poor crimps.

Another possibility is the engine dipstick tube stud ground point. The O2 sensor grounds there along with the ECU and a host of other sensors.

I've also had success with removing the ECU, spraying out the connections with a good electronics cleaner and then using a small pick to tweak the female connectors so they grab the pins more tightly.
 
As mentioned in many threads of mine (sorry i sometimes feel like im repeating myself) i have gone through this Jeep with a fine tooth comb. All sensor grounds are below 1 OHM resistance.. most are .5 OHMS or less. Grounds are not an issue on my Jeep.

I had a problem with my ECU where it was closing my IAC pintle all the way closed.. so now i even have a different computer in there with these same issues.

The only conclusion i have is that i am getting way WAY to much air into the intake when the throttle opens.. i mean i am using a Dodge Dakota TB which is very large (2001 era 4.7l ~68mm). The RENIX just cant keep up.

So besides a custom ECU like megasquirt what options are out there? Can i build something that could act like a map clamp on a NA vehicle? Could the TPS not be fast enough on these model years? Same with the Injector circuit?

Granted, a lean spike when you open the throttle is normal.. but if i do it just right especially after a start, i can drop it so lean that it will lose power (timing gets retarded).
 
Last edited:
What size is the throttle body? Renix TPS responds very quickly. I've watched it on a DRB. I can't see how your tip-in could be any more aggravating to fuel management than me stomping my foot to the floor from a dead stop with a 60mm throttle body.
 
Well that's weird. I don't think it's the TB size though. WOT is open loop and the oxygen sensor is disregarded by the ECU. I'd love to observe your O2 readings with a DRB or Snap-On Brick when this is happening.
 
Ive thought about it being a Slow 02.. i wonder if thats it. I have tried two new BOSCH's... without a different result.

Ive also thought about getting Snap On 2500... but i have been putting it off. Still cant find a DRB at all on ebay that doesnt cost way to much.

Was also in the process of building an Arduino board to read the RENIX data stream.. but i havent had any luck getting it to work unlike others.
 
An MT2500 would be handy. What if your O2 sensor isn't heating up or something?
Got any buddies in the aftermarket repair business? A six-pack might get you a scan.........
 
cruiser54 said:
An MT2500 would be handy. What if your O2 sensor isn't heating up or something?
Got any buddies in the aftermarket repair business? A six-pack might get you a scan.........
Click to expand...

Heating circuit is definitely working. Jeep gets to closed loop in 25 seconds on a cold start. Also verified at the sensor.

Dont have any buddies with one.. thought about trying the 6 pack thing.. but this is a rich beer town and no one ever seems to go for a trade... Honestly im doubting anything is "wrong" its just plainly not getting enough fuel or too much air.

I guess i will just live with it for now.
 
23lb hr injectors running stock fuel pressure and map adjusted over stock 5v to achieve optimal WOT AFR's. Tried the reverse on my RENIX (Higher fuel pressure and MAP voltage at stock or lower) and the ECU didnt like that combo as well as where its set at now. It was difficult to achieve proper WOT AFR's also.. so thats why i am set-up the way i am.
 
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